Materials Literature
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Recently, porous silicon has been extensively studied due to its luminescence properties and some interesting features for micromechanical technology, characteristics that have led to a wide range of applications, from electro-optical devices to IR radiation detectors and gas sensors. It is therefore very important to…
Hydrothermal investigations of the high silica region of the Na 2 O–Nd 2 O 3 –SiO 2 system, carried out in the search for new fast-ion conductors (FIC's), yielded the compound Na 3 NdSi 6 O 15 ·2H 2 O (sodium neodymium silicate). Single-crystal X-ray methods provided lattice constants of a = 7.385 (2), b = 30.831 (7)…
The experimental results of electrical conductivity temperature dependence and photoconductivity spectra studies of Sn2P2S6 ferroelectrics are reported. It is shown that dark electrical conductivity have two states—high-resistive (background) and low-resistive (induced by preliminary light irradiation). The results ar…
A modified kinetic Monte Carlo computer simulation has been developed and applied to the investigation of fiber (out-of-plane) texture formation in polycrystalline thin films grown in the absence of high-energy bombarding particles. Unlike high-energy deposition, in which texture formation appears to result from a com…
Crack/particle interactions in alumina/silicon carbide nanocomposites have been investigated by scanning electron microscopy and transmission electron microscopy, with cracks induced by Vickers microindentation. Intergranular cracks are frequently deflected into grains by SiC particles on grain boundaries inclined to…
An explanation is given for the narrow peak in the temperature dependence of the component α 32 of the magnetoelectric effect tensor near the transition at T = T c to the m ′ m 2′ phase observed in the boracites. A phenomenological approach is used which is based on the symmetry of the cubic phase of the crystals. The…
The self-diffusion of a particle on a flexible surface, such as a fluid bilayer membrane or a macroscopic interface, is analyzed theoretically in order to relate the macroscopic diffusion coefficient DM, describing displacements in a laboratory-fixed plane, to the intrinsic surface diffusion coefficient DS and to the…
Epoxidation of olefins by dioxygen in combination with aldehyde as reducing agent can be carried out at room temperature, in the absence of metal catalysts, using perfluorocarbons as inert reaction media. These non-toxic, non ozone-depleting fluids are good alternatives to the chlorinated solvents normally used.
Experimental data about the dependence of the Auger signal from crystalline samples on the primary beam direction are presented and discussed. It is shown that, for Auger electrons and elastically and inelastically backscattered electrons, maxima of the signal in its dependence on the polar and azimuth angles of the p…
The proteins encoded by the fructose-inducible lev operon of Bacillus subtilis are components of a phosphotransferase system. They transport fructose by a mechanism which couples sugar uptake and phosphoenolpyruvate-dependent sugar phosphorylation. The complex transport system consists of two integral membrane protein…
The synthesis, characterization, thermal, and dielectric properties of three different zwitterionic methacrylates of the sulfobetaine type are presented. Diethylamine-ethyl-, 2-(diethylaminoethoxy)-ethyl-, and 2-(2-diethylaminoethoxy) ethoxy-ethyl-methacrylates were made to react with butanosultone to prepare monomers…
Because the dipole moment of its zwitterionic side group is very high (μ∼23 D), poly[3-(N,N-diethyl-N-(5-methacryloyoxy-3-oxopentyl)-ammonio) propanesulfonate] affords a unique polar host matrix possessing a strong solvation power towards a variety of polar or ionic guest species. Water, glycerol, liquid ethylammonium…
Poly(γ-benzyl l -glutamate) (PBLG) was bonded covalently to a flat substrate, and it formed an aligned dipole layer (PBLG−CRA film). Using the PBLG−CRA film as an orienting film for a nematic hydrogen-bonded liquid crystalline complex, 6OBA−9Py (formed from 4-(hexyloxy)benzoic acid (6OBA) and 4-nonylpyridine (9Py)), c…
The anomalous responses of M w to conversion and to comonomer stoichiometry, i.e., deviations from expected classic A−A + B−B step-growth polycondensation behavior, observed in poly( p -phenylene sulfide) synthesis from p -dichlorobenzene and sodium sulfide are shown to be a consequence of unequal rate constants for t…
Particle morphologies for 2 and 3 wt% Pd/K L-zeolite have been determined using X-ray absorption spectroscopy (XAS). X-ray absorption near edge structure–temperature programmed reduction (XANES-TPR) was used to check for the presence of unreduced palladium cations in the locked cages after reduction. A series of calcu…
A unique desintering phenomenon has been observed in gas‐pressure sintering of silicon nitrides with additives of yttria and alumina. The desintering phenomenon occurred, simultaneous with weight increase, only when a boron nitride crucible was used in combination with the application of high nitrogen pressure (5 MPa)…
The polymorphism of sulindac was investigated. Two polymorphs (I and II) and a new crystalline form (form III) of sulindac were prepared by recrystallization in different solvents. In addition, three new pseudopolymorphs (solvates) from acetone, chloroform, and benzene were obtained, with each containing 1 mol of solv…
The development of photocured, water based, epoxy acrylate coatings to negate the deleterious effect surface flaws have on the strength of glass is reported. Strengthening of both (a) glass rods that have been damaged in a controlled fashion and (b) production line bottles is demonstrated. In both cases strengthening…
thin films of different thicknesses were deposited by the flash evaporation method onto cleaned glass plates held at room temperature. Structural characterization was carried out using x-ray diffraction and transmission electron microscopy which revealed that the films are polycrystalline and the grain size increases…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTHigh-Pressure NMR Studies of (Porphinato)iron-Catalyzed Isobutane Oxidation Utilizing Dioxygen as the Stoichiometric OxidantKevin T. Moore, István T. Horváth, and Michael J. TherienView Author Information Department of Chemistry, University of Pennsylvania Philadelphia…